Accurate Determination of Rare Earth Elements in USGS, NIST SRM, and MPI-DING Glasses by Excimer LA-ICP-MS at High Spatial Resolution

Abstract

ABSTRACT The effect of central gas flow rate (carrier gas and makeup gas) on signal intensities, ThO/Th, Th/U, memory effect, and interface pressures were investigated in this work. Detailed examination of the changing trend of fractionation index with different crater diameters from 8 µm to 60 µm reveals that rare earth elements (REEs) can also be classified into three groups: (1) La, Pr, Nd, and Sm (light REEs), (2) Ce, and (3) Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu (heavy REEs). In this work, REEs in MPI-DING glasses, USGS basaltic reference glasses, and the synthetic NIST glasses were determined at a high spatial resolution of 24 µm. The limits of detection for REEs at a spot size of 24 µm are within the range 0.003 to 0.030 µg g−1. Most of the determined values were found to be in excellent agreement with the reference values, with the relative error (RE) less than 10%. Our analytical precision, as given by the 1-s relative standard deviation (% RSD), is typically less than 15% for elements having concentration higher than 0.1 µg g−1, and there is a significant negative correlations between concentration and RSD on a logarithmic scale for these glasses, with logarithmic correlation coefficients being − 0.84. This expected trend of decreasing RSD with increasing concentration for these glasses indicates that the analytical precision follows counting statistics and thus that most of the data variation is analytical in origin and not due to chemical heterogeneities. Ce in GOR132-G is a notable exception, which has especially high RSD, and thus is possibly not homogeneously distributed.